Electric-resistance furnace.



W. D. COOLIDGE.

ELECTRIC ReslsrAnE FunNAcE.

APPLICATION FILED DEC.\.196.

Inventor:

William DCoolidgge,

' His Dttorneg.

UNITED STATES PATENT OFFICE.

WILLIAM D. COOLIDGE, OFSCHENECTADY, NEW YORK, AssIGNOn. TO GENERALELECTRIC COMPANY, a CORPORATION OF NEW Yonx. i

ELECTRIC-RESISTANCE rUnNAcE.

Snecma-,ation of Letters Patent.

'Patented June 4, 191.8.

Application nled December 16, 1918. Serial No. 137,354.

. sistance Furnaces, of which the following or other cooling fluild,admitted throughv lthe tube. At the opposite is a specification.

The present invention comprises a novel resistance furnace having aheater tube of refractory material, the object of the in* vention beingto provide a simple, rugged furnace capable of operation at temperaturesup to 2500o C., or more and adapted to maintain a' high vacuum or inertatmosphere about the object to be heated.

The novel features of my invention will be pointed out withparticularit-y in the appended claims and a detailed description of theinvention will be given in connection with the accompanying drawings of.which Figure l illustratespartly in perspective and partly in vert-icalsection a furnace embodying my invention, and Fig. 2 shows in sectiondetails of a terminal adjacent to the cover plate.

As shown in the drawing, the furnace comprises a heater tube 1 of highlyrefractoryy material, preferably tungsten, at one end of which is joineda plug 2 of a metal of high electrical and heat conductivityfor example,copper, which clges the end of end a ring 3 of like metal -is joined.The copper is preferably'rst treated while `fused with oxidizable boronmaterial to remove dissolved gasesand is then cast in a vacuum in con-ltact with the tungsten, as described in my prior Patent, No. 1,162,341.In this way an intimate molecular adherence of the two' metals issecured. Surrounding the heater tube and spaced away therefrom is aninclosing envelop or tank 4, which is provided with an outer jacket 5.affording a space through which a cooling uid may be circulated. On theOuter surface of the tank 4 spiral baffle plates 6 are located to causea circulation about the tank Of water a tube 7 and exhausted through atube 8. Between the' plugv 2 at the lower closed end of the heater tubeand the tank 4 is' provided a yielding or floating electricalconnection, preferably a body 9 0f liquid lmetal, such as mercury whichpermits expansion and contraction of the heater while preserving goodelectrical connection. A cooling y coil 10, immersed in the mercurymaintains a desired temperature during the operation of the furnace.Suitable gas`tight inlet and outlet tube of the cooling coil.

The Contact ring 3 is mechanically fitted within the end of a metal tube13 which passes through the cover plate 14 of the tank 4. The coverplate is maintained firmly pressed against the tank 4 by bolts 15,suitable insulating gaskets 16, 17 of fiber, rubber or the like, beingprovided to insulate the cover from the tank and the bolts 15. The coveris cooled by means of a coil 18, having an inlet tube 19 and an outlettube 20. vA contact plate v21 joined to the tube 13 is fastened to thecover plate 14 by bolts 22, suitable washers 23 of lead or the likebeing provided to make a gas-tight joint. A split clamping ring 24 bestshown-in Fig. 2 surrounds the tube 13 at .its junction with the packedcouplings 11, 12 are provided for the ring 3l on the open end of theheater. It is ythe tank may be evacuated or charged with gas through atube 28, and is shown as communicating with a vacuum pump through achamber 29 containing a drying agent 30 such as phosphorous pentoxid.The space 'Within the heater tube maybe se arately evacuated, or chargedwith gas. Vs indicated the end of the charging tube 13 is closed witha.v cylindrical 'stopper 31 communicating with a tube 3 2, and providedif desired with a window for observing the interior of the' heatertube Agasketl33 of u rubber secures a vacuum-tight jolnt.

l A heating current for the heater tube is i supplied by conductors 34,35, connected respectively to the tank 4 and thegcontact 21. A furnaceconstructed as above described with artificially.cooled electricalterminals in intimate contact with the heater and located within theinclosing tank, may

be heated up with great rapidity` with a siifliciently heavyl currentWithout weakening or increasing the electrical resistance of thecontacts.

What I claim as new and desire to secure by vLetters Patent of theUnited States, is: 1. An electric furnace comprising a heater tubefconsisting of refractory material, a

plug of metal of -good heat and electrical conductivity molecularlyjoined to and 'clos'-r ing one endof said tube, an inclosing'metal tankspaced apart from said heater tube, a

yielding electrical connection between said .A inclosed end of theheatertube and the tank,

an insulating -sealj between the opposite end of Vtheheaiter tube andsaid tank, and electrical connections respectively. for said tank, and-for the'end of' the heater tubeopposite the end in electrical contactwith said tank. 2. Anelectric furnace comprising a heater tube oftungsten, a plug` offcopper joined to and closing -one end of said tube,a copper contact ring joined .to the opposite open end cf said tube,- ametal tank inclosing said tube, a yielding electrical connection betweensaid plug and said tank, a metal cover f for said tank electrically incontact .with

` a conducting liquid between the opposite end4 of said tube and saidcasing, and'electrical said heater tube, an insulating seal between saidcover and said tank, and electrical connections respectivelyfor saidtank and said cover.

3. An electric furnace comprising a substantially gas-tight hea-ter tubeof refractory material, means for removing or intron` ducing gas to saidtube, means for conducting a heating current thereto, and a sealedinclosing envelop spaced apart from said vheater tube and adapted to beseparately evacuated or filled with gas.

' 4. A vacuum furnace comprising a heater tube of refractory material, ametallic casing'for said tube spaced apart therefrom, a quantity ofmercury in said cas-ing, means for cooling said mercury, a plug of goodconducting material joined to one end of said heater tube and contactingwith said j mercury, andvelectrical connections respec-"i tively n forthe oppositeend of said tube and for the metallic easing.

' 5. A furnace comprising a heater tube ofrefractory 'materiah al metalcasing spaced vapart therefrom, an insulating seal between one end ofysaid heater tube and said casing,

' from said casing.

connections respectively for saidlcasing and Ifor the lend of saidheater tube insulated 6. An electric Vfurnace comprising a resistor ofrefractory material inclosing a heating zone, a metal casing spaced awayvfrom said resistor comprising a tank and within said tank, lm'leans forartificially cooling said contacts, a. tube for introducing a charge tobe heated into said resistor tube communicating with said resistor tubeand projecting outside of said tank, and electrical connections for saidcontacts.

8. An electric fui-.nace comprising a tunesten'tube closed at one end,`a gas-tight casing surrounding said tube and spaced apart therefrom, aquantity of Aliquid metal in contact with the closed end of said tube, acharge-receiving tube electrically connected to the open end of saidtungsten tube and projecting through sa'id casing, means i forevacuating or filling with gasthe space between said Vtungsten tube andsaid casing independently of the space within said tube, and electricalconnections for the respective ends of said tungsten tube whereby acurrent for heating the tube may be conveyed.

9. An electric furnace comprising a gasimpervous refractory conductingtube i sealed at one end, means for introducing and withdrawing a chargeinto the opposite end thereof, a gas-tight casing surrounding said tubeand spaced away therefrom, a yielding electrical connection between theclosed end of said ytube and said casing, an

electrical connection to the opposite end of said tube and means forevacuating the space between said tube and said casing in` dependentlyof the. space within said tube.

In witness whereof, II have hereunto set inyhand this 14th day of Dec.,1916.

-l/VILLIAM D. COOLIDGE.

